This invention relates to a bulb socket for holding a wedge base bulb to supply electric power thereto.
One conventional socket for holding a wedge base bulb to supply electric power thereto is disclosed in Japanese Utility Model Unexamined Publication No. 2-47787. In this construction, a pair of metal members are attached to a socket body, and a supplying terminal portion and a resiliently-engageable portion, which are formed on each of these metal members, are exposed in a bulb insertion hole. When a base portion of the wedge base bulb is fitted in the bulb insertion hole, two power terminals mounted on the base portion are contacted respectively with the supplying terminals of the two metal members, so that electric power can be supplied to the wedge base bulb. At the same time, rugged portions formed on the base portion engage the resiliently-engageable portions of the two metal members, respectively, so that the base portion is held between the two resiliently-engageable portions to thereby prevent the wedge base bulb from withdrawal.
When attaching the wedge base bulb to the socket, it is desirable that a contact resistance at the area of contact between each supplying terminal and the associated power terminal be low, and it is also desirable that a resilient force at the area portion of contact between each resiliently-engageable portion and the associated rugged portion be large.
However, in the conventional construction, the supplying terminal portion, for supplying electric power to the wedge base bulb, and the resiliently-engageable portion, for holding the wedge base bulb, are formed as an integral metal member made of a single material. Therefore, the material of the metal member is required to perform both the functions of reducing the contact resistance and increasing the resilient force of the resiliently-engageable portion; however, there exists no material which achieve both functions effectively at low costs, and as a result both functions have not been entirely satisfactory.
In the meantime, a requirement for such a bulb socket, when used on a vehicle body, is that the amount of rearward projection of a light device should be reduced. Therefore, there is known a construction in which the other end of each metal member exposed in a bulb insertion hole is extended perpendicularly to the bulb insertion hole, so that the whole of the bulb socket assumes an L-shape.
In this case, the metal member is also of an L-shape, and hence can not be inserted into a casing through the bulb insertion hole after the casing is molded, and therefore there has been used a method (hereinafter referred to as "insert molding") in which a resin is molded on the periphery of the metal members while holding the metal members.
However, setting apart from the case where the metal member has a simple configuration, when the configuration is complicated as shown in the above-mentioned publication, such an insert molding is difficult because a gap may be formed between the metal member and a mold during the insert molding as a result of lowered dimensional accuracies, so that a resin flows into such a gap. In addition the metal members may interfere with the mold such that they cannot be sufficiently held by the mold. As a result, by an injection pressure, the metal members are deformed, and the resin is caused to flow. Furthermore, if the mold is complicated, it is difficult to feed the parts by a part feeder in an automated production.
It is an object of this invention to provide a construction in which functions of reducing a contact resistance at power supply portions for a wedge base bulb and securing a high holding force at those portions of engagement with the wedge base bulb are both achieved, and the manufacture can be carried out easily even if the configuration of the metal members is complicated.